[lvs-users] lvs NAT mode - real server to (different) virtual server public IP web requests fail

James H jeh1965 at gmail.com
Thu Nov 26 04:17:18 GMT 2009

Greeting LVS users,

I have an interesting issue I haven't been able to solve, please let
me know if I've missed a documented point. I have a fairly standard
LVS NAT setup for load balancing multiple websites to multiple
servers. But I have an interesting problem where one website needs to
call a web service on another website within the same LVS-NAT cluster
via the virtual server public IP interface. The real server outbound
request won't seem to go "full circle" out to the director and then
back into the other virtual server's public IP.

Consider this setup, where WebApp1 and WebApp2 are two websites on
separate public IP addresses.

WebApp1       WebApp2
       LVS NAT Director
RealSrv1 RealSrv2 RealSrv3

Request comes into WebApp1 Public IP
---> LVS Nat Director
    ---> NAT RealSrv1
    WebApp1 running on RealSrv1 needs to call a web service on WebApp2
(Public IP)

I cannot seem to get RealSrv1 to call the web service of WebApp2. For
that matter even trying to load WebApp2 on lynx on any of the real
servers fails.

I was able to briefly solve this issue by setting up an intermediary
server that is connected to both the private and public networks, and
putting a static route to the public IPs subnet on the RealServers to
communicate through the intermediary. It works for about 10 seconds,
then it dies.


james h

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